The present invention relates to a method and apparatus for a motor fluid drainage interface, and more particularly to apparatus and methods for production of an electric motor fluid drainage interface.
Electric Motors are the prime movers for most industrial applications. In industry, most motors are used in conjunction with speed changing devices which change the speed or torque produced at the motor shaft to match the speed or torque required by the driven equipment such as pumps, fans, conveyors, etc.
One of the most common speed changing devices is a speed reducer, or gearbox, which consist of a set of gears encased by a housing and partially immersed in lubricating oil. Oil is necessary in order to reduce friction between the gears and to allow the bearings in the gearbox to function properly. The oil leakage from the gearbox housing is prevented by oil seals.
An electric motor may be connected to a gearbox in a variety of configurations, with the particular arrangement being dictated by the intended use of the motor and gearbox. The ultimate operating position of the motor could be horizontal, vertical-shaft down, or vertical-shaft up. The application requirements and space restrictions normally dictate which position is required. Most motor manufacturers and gearbox manufacturers do not recommend mounting the motor vertical-shaft up when the two components are put together, because such an arrangement increases the likelihood of oil escaping from the gearbox and entering the motor.
While oil is necessary for a gearbox to function properly, it is detrimental to electric motors. If oil is allowed to enter an electric motor, the oil may cause fouling within the motor, may cause the coils within the motor to short-circuit, and may pose an additional risk as a fire hazard. Oil seals, such as those in a gearbox eventually fail, some sooner than others. Some motors designed for high volume requirements have multiple seals on the motor shaft for added protection, but the risk of seal failure still exists.
Electric motors are often mounted to gearboxes by use of C-Face flanges. The term xe2x80x9cC-Facexe2x80x9d refers to a set of dimensions, promulgated by the National Electrical Manufacturers Association (NEMA), which are used to standardize the way in which electric motors are attached to motor driven equipment. On a C-Face compatible motor, the shaft end endbell of the motor is machined to specific dimensions with predetermined bolt holes, bolt circle, and pilot diameter, etc. Each item of C-Face compatible motor driven equipment has a machined flange (a C-Face flange) which accepts the dimensions of the motor, allowing the motor and the driven equipment to be mated and bolted together. The connection of C-Face compatible components is known as C-Face mounting.
The shaft of a motor connected to a gearbox with a C-Face flange is not open to the environment. Therefore, any oil leaking from a gearbox into the motor is not obvious to an observer until evidenced by failure of the motor.
Motor failure caused by oil intrusion often necessitates replacement of the motor at a cost of $100 to $2000 depending on the horsepower, design, and enclosure of the motor. Motor failure caused by oil intrusion also results in innumerable hours of down time and lost production, as well as the costs of gearbox damage caused by the undetected loss of lubricating oil.
A need, therefore, exists for an improved drainage interface which is capable of being placed between an electric motor and gearbox, particularly when the motor is vertical shaft-up oriented, which prevents oil escaping the gearbox from entering and causing damage to the electric motor, and which further transports oil outside of the motor/gearbox assembly to be observed as an indication that maintenance need be performed.
Applicant is aware of the following U.S. Patents concerning drainage interfaces for electric motors.
Baker et al., U.S. Pat. No. 4,689,511 teaches a drain structure for a vertically mounted electric motor positioned below a liquid sump into which the rotor shaft of the motor can be connected including a drip pan through which the rotor shaft passes, the pan having peripheral side walls and drain means attached thereto and a liquid slinger above the pan adapted to sling liquid leakage in a radially outward direction below the pan side walls to be drained away from the motor. However, the ""511 invention simply rests upon the endshield of the motor and does not facilitate the connection of the electric motor to other equipment. Specifically, the ""511 invention does not provide standardized mounting means, nor mating means to aid in alignment of the motor shaft with the drain structure and other connected equipment.
Baker, U.S. Pat. No. 4,992,690 teaches an electric motor for use with a pump having a stator and rotor assembly. The rotor assembly includes a rotatable shaft and a rotor affixed to and rotatable with the shaft. The stator and rotor assemblies are intended for installation in an appliance. A cover forms an endshield for the motor, as well as a portion of the housing of a pump for the appliance. The cover is so constructed to align the shaft extending into the pump with operable portions of the pump. The motor discloses a drain for collecting and draining water away from the motor shaft. However, the disclosed motor is a self-contained unit for connection directly to a pump. The ""690 motor, therefore, may not be used as an interface between a standardized motor and pump or gearbox assembly.
The invention provides an apparatus for mating a vertically oriented electric motor underneath a gearbox or other motor driven apparatus which substantially isolates the motor rotor and driven shaft from the external environment while facilitating the removal of leaking oil or other fluid from the area between the motor endshield and gearbox housing. The invented interface, in use, resides between a vertically oriented electric motor and a gearbox or other motor driven device containing oil or other fluid.
The apparatus consists of two main parts, a base plate and a flinger. The substantially flat, circular base plate has an aperture through its center. The base plate defines oil exit ports, which are small diameter ports that extend through the body of the base plate, from the top of the base plate near the outer diameter of the aperture, to the outside edge of the base plate. The base plate also has a raised portion on its upper surface and a recess on its lower surface to provide for connection and alignment of the interface with the motor and gearbox.
The flinger is a ring shaped object having an inner diameter corresponding to the outer diameter of the electric motor rotor shaft.
When attached between an electric motor and a piece of motor driven equipment, the base plate rests upon and is attached to the endshield of the vertically oriented electric motor. The base plate is positioned so that the aperture of the base plate is coaxial with the motor rotor shaft, with the rotor shaft protruding upwards through the aperture. The recess in the lower surface of the base plate, and a series of bolt receiving holes around the periphery of the base plate intimately mate and attach to the endshield, preferably by means of a C-Face flange type connection.
The flinger is positioned around the portion of the rotor shaft which extends through the body of the base plate. The flinger is positioned along the rotor shaft just above the body of the base plate. An oil seal is preferably installed in the region between the outer diameter of the rotor shaft and the inner surface of the base plate aperture. The base plate and electric motor are then attached to the fluid containing gearbox or other device, preferably by means of a C-Face flange type of connection.
In use, the flinger rotates with the rotor shaft when the motor is in operation. In the event of oil seal failure in the gearbox, escaped oil flows downwardly along the rotor shaft or in close proximity thereto. The oil encounters the spinning flinger which projects the oil outwardly, away from the rotor shaft, and therefore away from the base plate aperture where the oil would possibly enter the inside of the motor. As the oil collects away from the motor opening, the oil escape ports facilitate the flow of the escaped oil away from the aperture area to the exterior of the interface.
The projection of leaking oil to the outside of the motor/gearbox assembly serves several functions. First and foremost, leaking oil is not given the opportunity to enter the underlying electric motor, preventing problems such as shorting, corrosion, and fire. Second, oil on the outside of the motor housing, or in another suitable holding means, is a clear indicator of malfunction, allowing otherwise undetectable seal leakage problems to be noted and repaired before equipment failure.
The principal object of the present invention is to provide an improved fluid drainage interface to prevent the accidental introduction of oil or other fluid into an electric motor when the electric motor is vertically mounted underneath fluid containing motor driven equipment.
A further object of this invention is to provide an improved fluid drainage interface to allow diagnosis of a fluid seal malfunction before failure of the fluid containing equipment or the connected electric motor.
Another object of the invention is to provide an improved fluid drainage interface to allow diagnosis of oil seal malfunction before failure of the oil containing equipment or the connected electric motor.
Another object of the invention is to provide an improved fluid drainage interface which may be connected to standard industrial electric motors and motor driven equipment using C-Face flanges, for use in an extremely wide variety of applications, and which may be produced at relatively low cost in small quantities.